What should we learn, English as lingua franca or “formal” English?

English is a dominant or official language in most of the parts of the world and speaking it is basic. But when the question is what we should learn I think both are important. It depends in what we are going to do, The English as a lingua franca (ELF) is a form that has become essential for communicating with other’s whose first language is not English, and the fact is that now with this, English is changing because people speak it the way they find it easier so the real dialect gradually disappeared. So it is the easiest way but not the correct one, that’s why as a conclusion the better way to learn is the formal English that way we can sometimes make use of the ELF words although we know the right way to write it.